Why data is encrypted

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Why is a private message encrypted before it is sent?

A So anyone who intercepts it cannot read it

B So it travels across the internet faster

2. Which statement about encryption is correct?

A It stops anyone from ever stealing the data

B It makes data unreadable to anyone without the key

3. A website stores your password. What should it do?

A Store it in encrypted form

B Store it as plain readable text

4. You type your bank details into a shopping site. Why does the site encrypt them?

A To keep them private while they travel over the network

B To make the payment cost less

5. Who can read encrypted data?

A Anyone who can see the data

B Only a person who has the correct key

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1encrypt(message, key)		AProtects card and account numbers so a thief cannot use them if they steal the data
2encrypt(bankDetails, key)		BThe password is sent as readable plaintext, so anyone who intercepts it can read it. It should be encrypted first, for example send(encrypt(password, key)).
3Encrypting a password before it is stored means a hacker who steals it sees only scrambled text		Cstored = encrypt(password, key)
4Only a person with the key can turn scrambled data back into private information		DScrambles a private message so only someone with the key can read it
5send(password) # plain text, no encrypt		ESharing the key publicly lets anyone decrypt the message, so encryption no longer keeps it private. The key must stay secret.
6encrypt(message, key) share(key) # tell everyone the key		Fdecrypt(ciphertext, key)

Definitions

encrypt

Fill in the Blanks

Complete each line of code by filling in the missing parts.

scrambled = _______(message, key)

readable = _______(scrambled, key)

safePin = encrypt(bankPin, ___)

__ dataIsPrivate: data = encrypt(data, key) send(data)

ciphertext _ encrypt(password, key)

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A data ← "bank details"

B IF data is public THEN

C data ← encrypt(data, key)

D END IF

Question 2

A password ← "cat123"

B key ← "Qm4z"

C stored ← decrypt(password, key)

D save(stored)

Question 3

A message ← "See you at 5"

B key ← "T9r2"

C coded ← encrypt(message, key)

D send(message)

Question 4

A ciphertext ← "PIN is 4821"

B key ← "Zx81"

C ciphertext ← encrypt(plaintext, key)

Question 5

A reason ← "show data to everyone"

B IF thief steals the data THEN

C thief needs the key to read

D END IF

Answer Key

Why data is encrypted

Section A: Quick Questions

A — So anyone who intercepts it cannot read it

B — It makes data unreadable to anyone without the key

A — Store it in encrypted form

A — To keep them private while they travel over the network

B — Only a person who has the correct key

Section B: Match the Pairs

encrypt(message, key) → Scrambles a private message so only someone with the key can read it

encrypt(bankDetails, key) → Protects card and account numbers so a thief cannot use them if they steal the data

Encrypting a password before it is stored means a hacker who steals it sees only scrambled text → stored = encrypt(password, key)

Only a person with the key can turn scrambled data back into private information → decrypt(ciphertext, key)

send(password) # plain text, no encrypt → The password is sent as readable plaintext, so anyone who intercepts it can read it. It should be encrypted first, for example send(encrypt(password, key)).

encrypt(message, key) share(key) # tell everyone the key → Sharing the key publicly lets anyone decrypt the message, so encryption no longer keeps it private. The key must stay secret.

Section C: Definitions

encrypt — To scramble data so nobody can read it without the key. This keeps private things like messages, passwords and bank details safe if someone steals or intercepts them.

Section D: Fill in the Blanks

scrambled = encrypt(message, key)

readable = decrypt(scrambled, key)

safePin = encrypt(bankPin, key)

if dataIsPrivate:
    data = encrypt(data, key)
    send(data)

ciphertext = encrypt(password, key)

Section E: Spot the Error

B — Encryption is used to protect private data such as bank details. The condition should check that the data is private, not public.

C — To keep a password private when it is stored, it must be scrambled with encrypt. decrypt is used later to turn ciphertext back into readable text.

D — This sends the plaintext message, so anyone who intercepts it can read it. It should send the encrypted version: send(coded).

A — Readable data is called plaintext. Ciphertext is the scrambled result. Line 3 uses plaintext, so line 1 should be plaintext ← "PIN is 4821".

A — The reason for encrypting data is to keep it private, not to show it to everyone. It should be reason ← "keep data private".